Re-usable schemas should use additionalProperties:true, so the schema
using it will check for evaluated properties.

Fixes: e2391782 ("spi: dt-bindings: split peripheral prods")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220810131236.428529-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>